Pursuant to 37 C.F.R. xc2xa7 1.71(e), Applicants note that a portion of this disclosure contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
Accurate measurements of distances are often critical to the proper performance of a given process or to the quality of a given product. For example, the manufacture of microfabricated devices, such as integrated circuits, microprocessors, microfluidic components, among many others, can require very high levels of accuracy in all aspects of the fabrication process, including fabricated device dimensions, in order to reliably produce the assorted microscale features of these devices. Many non-microscale devices similarly must be efficiently manufactured with dimensions accurately produced according to specifications in order to achieve cost effectiveness.
In the context of microfluidics, for example, these devices generally provide high-throughput methods of performing diverse instrumental analyses, including various cell-based screening and separation assays of particular relevance to modern pharmaceutical discovery. Many of these assays generate detectable signals by passing fluorescently labeled cells through laser induced illumination spots incident within device cavities. Accurately measured illumination spot widths are important for interpreting data obtained from cell-based or other assays. Specifically, an improperly focused illumination spot having a width smaller than the cavity width at the point of incidence typically yields biased results, such as incorrect ratios of the number of labeled to unlabelled cells. Furthermore, knowledge of accurate illumination spot sizes allows the velocity of cells flowing through the cavity to be more easily calculated.
Accordingly, improved methods of measuring distances in microfluidic systems would be desirable. The present invention is directed to these and other features by providing methods of measuring widths of illumination spots as well as other distances. The invention also relates to systems and software for performing the methods of the invention. These and many other features will be apparent upon complete review of the following disclosure.
The present invention generally relates to measuring distances. In particular, the invention provides methods, and related systems, for measuring widths of illumination spots and distances between two points (e.g., between two detectable marker points), and for predicting detected signal widths. In preferred embodiments, measurements of various microscale cavity dimensions, including those of microfluidic devices are made according to the methods described herein. For example, illumination spot measurements are typically utilized to optimize various microfluidic applications, such as cellular-based assays, by focusing or defocusing illumination spots used for detection to correspond to cavity dimensions at the points of illumination spot incidence. Software products for performing the methods of the invention are also provided.
In one aspect, the invention relates to a method of measuring a width of an illumination spot. The method includes passing (e.g., manually, robotically, or the like) the illumination spot (e.g., generated by a laser, etc.) across two points at a rate, where a distance between the two points is known, and in which a detectable signal is created as the illumination spot is incident across each of the two points. In preferred embodiments, identical or different components of a microscale cavity (e.g., a microchannel, a capillary channel, a microscale reservoir, or the like) include the two points (e.g., two sides of a microchannel or the like). The method also includes measuring an amount of time for the illumination spot to move from a first of the two points to a second of the two points (e.g., through and between each of the two points), and calculating the width of the illumination spot from the amount of time, the rate, and the known distance between the two points (e.g., a width of a microchannel, etc.). The calculating step typically includes multiplying the rate and the amount of time to yield a detected signal width, and subtracting the distance between the two points from the detected signal width. The method generally further includes focusing or defocusing the illumination spot upon measuring the width of the illumination spot to correspond to about the distance between the two points. For example, the focused or defocused illumination spot is optionally utilized to optimize detection of an assay (e.g., a cell-based assay or the like) performed in a microfluidic device.
In another aspect, the invention provides a method of measuring a distance between two points, such as two sides of a microchannel (e.g., a width of a microchannel, etc.) or the like. The method includes passing (e.g., manually, robotically, or the like) an illumination spot (e.g., generated by a laser, etc.) across the two points at a rate, where a width of the illumination spot is known, and in which a detectable signal is created as the illumination spot is incident across each of the two points. In preferred embodiments, identical or different components of a microscale cavity (e.g., a microchannel, a capillary channel, a microscale reservoir, or the like) include the two points. The method also includes measuring an amount of time for the illumination spot to move from a first of the two points to a second of the two points, and calculating the distance between the two points from the amount of time, the rate, and the known width of the illumination spot. The calculating step typically includes multiplying the rate and the amount of time to yield a detected signal width, and subtracting the width of the illumination spot from the detected signal width.
In yet another aspect, the invention relates to a method of predicting a detected signal width expected upon detecting a detectable signal created as an illumination spot passes across two points, where a width of the illumination spot and a distance between the two points are known. The method includes summing the width of the illumination spot and the distance between the two points.
The present invention also provides a system that includes a computer and system software having one or more logic instructions for performing the methods described herein. In addition, the invention also relates to a software product that includes a computer readable medium having a computer program stored thereon for causing a computer to measure a width of an illumination spot or to measure a distance between two points.